A drive unit for adjustable beds, such as hospital beds and the like, of the type which have movable head and leg sections, and/or other adjustment functions, and comprises a unidirectional, rotary motor, and a drive shaft for each adjustable bed function. Gears are rotatably mounted on each of the drive shafts, and are rotated thereon in opposite directions by the motor. A pair of spring clutches are operably associated with their associated shafts to rotate the shafts, and thereby adjust the position and/or configuration of the bed.
For many years, hospital beds have had movable parts, such as an upper body support part movable between two positions in which it supports the patient in a sitting position and a prone position. Movement of these parts originally was effected manually by hospital personnel, for example by turning a crank provided on the bed.
Motorized operated hospital beds are conventional in which the head and leg sections of an articulated frame can be adjusted to a desired inclination by one or more motors. In this fashion, a patient's back or legs can be adjusted to a desired inclination. The actuating mechanism for the head section of the articulated mattress frame may include an electric motor which rotates an elongated threaded shaft. A nut is threadably mounted for longitudinal movement along the shaft and is fixed against rotation relative thereto. Thus, rotation of the shaft produces longitudinal travel of the nut. A linkage interconnects the nut and the head section of the articulated frame in such a way as to convert longitudinal motion of the hut into rotational movement of the head section, thereby altering the inclination of the latter. The motor can be deactivated at any time to hold the head section in a given position of adjustment.
U.S. Pat. No. 4,559,655 describes the conventional motorized hospital bed in which the head and leg sections of an articulated frame can be selectively raised and lowered by two or more electric motors. In this fashion, a patient's back and/or legs can be adjusted to a desired inclination. The actuating mechanism for the head section of the articulated mattress frame may include and electric motor which rotates an elongated threaded shaft. A nut is threadedly mounted for longitudinal movement along the shaft and is fixed against rotation relative thereto. Thus, rotation of the shaft produces longitudinal travel of the nut. A linkage interconnects the nut and the head section of the articulated frame in such a way as to convert longitudinal motion of the nut into rotational movement of the head section, thereby altering the inclination of the head section. The motor can be deactivated at any time to hold the head section in a given position of adjustment.
It is well known that hospital and home care and convalescent-type beds, having independently moveable articulated head, knee and leg sections are connected to independent drive mechanisms and motors. U.S. Pat. No. 4,970,737 teaches us that the adjustable hospital and nursing home bed, has a three-part support frame for mattresses, the head, middle and foot part of which are pivotably connected to one anther via pivot shafts and are supported in a suspension frame of a bed frame such that they are pivotable in height directly by means of a force provider via a lever linkage.
U.S. Pat. No. 5,317,769 teaches a hospital bed having two mechanical drive mechanisms connected between each end of a bed support frame and a base, each of which has a respective actuator. Selective operation of each of the drive mechanisms with the actuators permits either end of the bed support frame to be raised or lowered to a desired position.
U.S. Pat. No. 4,425,674 teaches a transmission for an adjustable hospital bed for positioning the bed in a plurality of different positions, the different parts of the bed moving independently and/or simultaneously, the transmission transmitting power to the adjustment mechanisms from a single common drive. The drive motor is stationary or fixed, however, increasing the complexity as well as the likelihood for mechanical failure of the resultant required apparatus.
U.S. Pat. No. 4,472,846 further teaches that different hospital bed functions or adjustments may be made by employing a single reversible motor to drive selected ones of a series of adjusting mechanisms. A bedside control unit for a hospital bed is operable from a position within the bed and also from a bedside chair, as found in U.S. Pat. No. 5,542,138.
U.S. Pat. No. 5,195,198 teaches a hospital bed which has a movable section, a selectively actuable drive arrangement for moving the section, a manually actuable control switch, and a control circuit coupled to the switch and drive arrangement. The control circuit includes a microprocessor having an input coupled to the control switch and having an output, and the program executed by the microprocessor selectively actuates the output of the microprocessor based on a function which takes into account the current state of a signal being applied to the microprocessor input.
Thus, as shown by the foregoing brief review of the prior art, each mode of adjustability, i.e., bed section function, is typically powered by a small, separate gear motor. Since these small motors are relatively expensive and have comparatively little actual running time during the effective life of the bed, such designs are expensive and inefficient. Multiple motors also increase the weight of such beds.
Typically, due to lowered reimbursement rates, guidelines and schedules established by the federal government, beds in use for home care and home convalescence, as well as beds used in hospitals, nursing facilities and other commercial facilities have only two motors, one for raising and lowering the head of the bed and one for raising and lowering the foot of the bed. A hand crank is used to raise and lower the overall height of the bed. As a result, it has been estimated that hundreds if not thousands of injuries occur nationwide on a yearly basis. Patients and their caregivers are injured attempting to move the patient from an improperly adjusted bed. Additional work is required of a caregivers to manually adjust the height of the bed prior to attempting to maneuver the patient, or have the patient move himself or herself. A third motor can also be used for adjusting the overall height of the bed, adding to cost, weight and gear complexity.